Scanning probe assisted localized CNT growth

Abstract

The present invention is a method for localized chemical vapor deposition (CVD) for localized growing for example for carbon nanotubes (CNT), nanowires, and oxidation using a heated tip or an array of heated tips to locally heat the area of interest. As the tips moved, material such as CNTs grows in the direction of movement. The Scanning Probe Growth (SPG) or nanoCVD technique has similarities to the CVD growth; however it allows for controlled synthesis and direction and eliminates the need for masks.

1. A method of localized chemical vapor deposition for generating nanostructures and microstructures, the method comprising:
 placing a substrate in a chamber; 
 bringing a movable apparatus with a sharp tip in contact with or at a constant distance from the substrate; 
 wherein said movable apparatus includes an electrical conductor; 
 reducing the pressure of said chamber to below atmospheric pressure using a pump connected to said chamber; 
 passing an electric current through said electrical conductor thereby heating said tip to a specific temperature by resistive heating; 
 heating the substrate by means of conduction or convection heat transfer from the tip to the substrate; 
 introducing at least one carrier gas in the chamber; 
 introducing at least one precursor gas in said chamber to cause a chemical reaction on the surface of said substrate; 
 moving said substrate and said tip relative to each other; and 
 generating a structure. 
 
     
     
       2. A method of localized chemical vapor deposition for generating nanostructures and microstructures, the method comprising:
 placing a substrate in a chamber; 
 bringing a movable apparatus with a sharp tip in contact with or at a constant distance from the substrate; 
 wherein said movable apparatus includes an electrically conducting object; 
 lowering the pressure of said chamber to below atmospheric using a pump connected to said chamber; 
 passing a high-frequency alternating current through an electromagnet in proximity to said electrically conducting object thereby heating said tip to a specific temperature by induction heating; 
 heating the substrate by means of conduction or convection heat transfer from the tip to the substrate; 
 introducing at least one carrier gas in the chamber; 
 introducing at least one precursor gas in said chamber to cause a chemical reaction on the surface of said substrate; 
 moving said substrate and said tip relative to each other; and 
 generating a structure. 
 
     
     
       3. The method according to  claim 1  or  2 , wherein the sharp tip comprises a one or two dimensional array of tips. 
     
     
       4. The method according to  claim 1  or  2 , wherein at least one catalyst is deposited on said substrate prior to inserting substrate in the chamber. 
     
     
       5. The method according to  claim 1  or  2 , wherein the tip shape is a polygon with a cross-sectional width between one micron and one nanometer. 
     
     
       6. The method according to  claim 1  or  2 , wherein the step of moving said substrate and said tip relative to each other is a vertical movement, generating a vertically aligned structure on said substrate. 
     
     
       7. The method according to  claim 1  or  2 , wherein the step of moving said substrate and said tip relative to each other is a vertical and horizontal movement, generating a three-dimensional structure on said substrate. 
     
     
       8. The method according to  claim 1  or  2 , wherein said tip temperature is raised and lowered in a predetermined manner. 
     
     
       9. The method according to  claim 1  or  2 , wherein said tip temperature is lowered gradually to anneal the nanostructure in contact with the tip. 
     
     
       10. The method according to  claim 1  or  2 , wherein said tip is heated and cooled to alternate growth and annealing steps. 
     
     
       11. The method according to  claim 1  or  2 , wherein said tip is used to grow a nanowire to connect two structures on said substrate. 
     
     
       12. The method according to  claim 1  or  2 , wherein an electric field is applied between said tip and said substrate. 
     
     
       13. The method according to  claim 1  or  2 , wherein said substrate is placed on a variable temperature plate to apply specific temperature. 
     
     
       14. The method according to  claim 1  or  2 , wherein an electric field is applied between two sides of the substrate. 
     
     
       15. The method according to  claim 1  or  2 , wherein said movable apparatus is a micromachined cantilever beam with an electrical conductor and a sharp tip at the distal end of said cantilever beam, said apparatus is attached to a micromanipulator, and said substrate is placed on an XYZ stage. 
     
     
       16. The method according to  claim 1  or  2 , wherein said movable apparatus is a micromachined cantilever beam with a sensing element on said cantilever to monitor the tip movement in relation to the substrate, wherein said sensing element is piezoresistive or piezoelectric. 
     
     
       17. The method according to  claim 1  or  2 , wherein the apparatus further comprises means to monitor the tip movement in relation to the substrate, the means selected from the group consisting of: a laser light directed to said apparatus and a photodetector to detect the reflected said laser light from the apparatus, an atomic force microscope, a triangulation displacement meter, a confocal displacement meter, a scanning electron microscope, an optical microscope, and an interferometer. 
     
     
       18. The method according to  claim 1  or  2 , wherein said precursor gas is a hydrocarbon, an organometal, an organic material, or other material capable of growing on the substrate a grown material, wherein said grown material is selected from the group consisting of: dielectrics, titanium nitride, SiO2, silicon-germanium, silicon, silicon oxynitride, silicon nitride, silicon carbide, carbon nanotubes, carbon fiber, metals, and synthetic diamonds. 
     
     
       19. The method of  claim 1  or  2 , wherein said tip is metallic or it is coated with a metal film.